Plant water potential and pressure balance
Osmotic and mechanical contributions together determine passive water movement.
Key knowledge
Water potential expresses water's potential relative to a specified pure-water reference in pressure units. Plant models distinguish solute, pressure, gravity and matrix contributions. Under passive isothermal exchange, water tends from higher to lower total water potential; a positive pressure contribution can oppose the negative solute contribution. Concentration alone therefore does not determine flow through a turgid plant cell.
Values and equations
Psi = Psi_s + Psi_p + Psi_g + Psi_m
- Psi
- total water potential relative to the stated reference Pa
- Psi_s
- solute contribution Pa
- Psi_p
- mechanical-pressure contribution Pa
- Psi_g
- gravitational contribution for the chosen reference elevation Pa
- Psi_m
- matrix contribution in the conventional decomposition Pa
Conditions and scope
- State the reference temperature, pressure and elevation; compare compatible total potentials and include relevant mechanical constraints.
- The additive decomposition is the conventional plant-water model. Gravity depends on chosen elevation reference, and matrix effects and nonideal solutions require their own treatment.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Inspected §30.5 Water Potential, solute and pressure bodies and the additive equation. Explicitly excludes the page's 'gravity always negative' wording and erroneous -0.1 MPa/m scale, simplistic solute hydrogen-bond explanation and unconditional soil-to-root gradient claim.
2026-10-10 · Independent Mathematics and Information editor (/root/core_math_information). Independent AI editorial review of this entry's statements, equations, applicability conditions and source coverage. Source checks apply to these claims within their stated limits.
Entry details
Permanent link to this entry ↗- Record identity
- foundation-bio-plant-water-potential
- Revision
- foundations-refresh.1
- Structured reference record
- Foundational reference additions